A5031101386- Gyrotron and Vacuum Electronics Research
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Magnetic confinement fusion research
- Electromagnetic Simulation and Numerical Methods
- Ionosphere and magnetosphere dynamics
- Microwave Engineering and Waveguides
- Superconducting Materials and Applications
- Particle Accelerators and Free-Electron Lasers
- Pulsed Power Technology Applications
- Semiconductor materials and devices
- Fusion materials and technologies
- Laser-Plasma Interactions and Diagnostics
- Electrostatic Discharge in Electronics
- Dust and Plasma Wave Phenomena
- Acoustic Wave Resonator Technologies
- Radio Frequency Integrated Circuit Design
- High voltage insulation and dielectric phenomena
- Electromagnetic Scattering and Analysis
- Antenna Design and Analysis
- Photocathodes and Microchannel Plates
- Diamond and Carbon-based Materials Research
- Nuclear Physics and Applications
- GaN-based semiconductor devices and materials
- Electron and X-Ray Spectroscopy Techniques
Tech-X Corporation (United States)
2015-2024
Brookhaven National Laboratory
2009-2015
Princeton Plasma Physics Laboratory
1987-2013
Oak Ridge National Laboratory
2009-2010
General Atomics (United States)
2010
University of California, Irvine
2010
Massachusetts Institute of Technology
2010
University of Wisconsin System
2009
University of Wisconsin–Madison
2009
Princeton University
1987-2009
A two-dimensional integral full-wave model is used to calculate poloidal forces driven by mode conversion in tokamak plasmas. In the presence of a magnetic field, near ion-ion hybrid resonance dominated transition from fast magnetosonic wave slow ion cyclotron wave. The field generates strong variations parallel spectrum that cause damping narrow layer surface. resulting this drive sheared flows comparable those direct launch Bernstein experiments.
Magnet design codes, plasma dispersion solvers, and particle-in-cell (PIC) simulation codes have been used to arrive at the first step in of an advanced ion source based on electron cyclotron resonance (ECR) technology. The concept uses a minimum-B magnetic mirror geometry which consists multicusp field assist confining radially, flat central for tuning ECR resonant condition, specially tailored fields end zones confine axial direction. is designed achieve axially symmetric ‘‘volume’’ with...
We develop a methodology for the design of multiple-cavity klystron interaction circuits. demonstrate our approach with detailed collector and four-cavity circuit multiple-beam (MBK) operating in fundamental mode at center frequency 3.27 GHz (S-band). These elements are designed to be used 32-A 45-kV magnetically shielded eight-beam electron gun currently under fabrication . Upon integration gun, circuit, collector, MBK will beam transport beam-wave studies validate developmental codes...
Simulation of dense plasmas in the radiofrequency range are typically performed frequency domain, i.e., by solving Laplace-transformed Maxwell’s equations. This technique is well-suited for study linear heating and quasilinear evolution, but does not generalize well to nonlinear phenomena. Conversely, time-domain simulation this difficult because time scale long compared electron plasma wave period, addition, various cutoff resonance behaviors within insure that any explicit...
A computational scheme is developed which permits tractable calculation of three-dimensional full-wave solutions to the Vlasov-Maxwell equations under typical ion cyclotron range frequencies (ICRF) experimental conditions. The method unique in that power deposition plasma determined via anti-Hermitian part a truncated warm dielectric operator, rather than as result an assumed phenomenological collision frequency. resulting computer code allows arbitrary variation density, temperature,...
The next step toward fusion as a practical energy source is the design and construction of ITER [R. Aymar et al., Nucl. Fusion 41, 1301 (2001)], device capable producing controlling high-performance plasma required for self-sustaining reactions, i.e., “burning plasma.” relies in part on ion-cyclotron radio frequency power to heat deuterium tritium fuel temperatures. In order effectively, wave fields must couple efficiently dense core plasma. Calculations this paper support argument that will...
Nonlinear effects associated with the physics of radiofrequency wave propagation through a plasma are investigated numerically in time domain, using both fluid and particle-in-cell (PIC) methods. We find favorable comparisons between parametric decay instability scenarios observed on Alcator C-MOD experiment [J. C. Rost, M. Porkolab, R. L. Boivin, Phys. Plasmas 9, 1262 (2002)] PIC models. The capability models to capture important nonlinear characteristic wave-plasma interaction (frequency...
The nonlocal Vlasov-Maxwell dielectric response kernel, K(r,r'), is constructed by integration along particle orbits in a nonuniform magnetic field. phase integrals comprising the usual plasma dispersion function are altered, and contain parameter characterizing parallel field gradient. We numerically solve 1D integral wave equation, including gradient, describing propagation, mode conversion, absorption physics. Significant changes found for...
Magnetically confined plasmas can contain significant concentrations of nonthermal plasma particles arising from fusion reactions, neutral beam injection, and wave-driven diffusion in velocity space. Initial studies one-dimensional experimental results show that energetic ions significantly affect wave propagation heating the ion cyclotron range frequencies. In addition, these absorb power at high harmonics frequency where conventional two-dimensional global-wave models are not valid. this...
Results obtained from experiments utilizing high-power ion cyclotron range of frequencies (ICRF) heating to stabilize sawtooth oscillations on Tokamak Fusion Test Reactor (TFTR) [Hawryluk et al., Plasma Phys. Controlled 33, 1509 (1991)] are reviewed. The key observations include existence a minimum ICRF power required achieve stabilization, dependence the stabilization threshold relative size deposition profile q=1 volume, and peaking equilibrium pressure current profiles during...
Global wave solutions with self-consistent velocity distributions are calculated for ion cyclotron heating in non-Maxwellian plasmas. The all-orders spectral algorithm (AORSA) global solver is generalized to treat non-thermal arising from fusion reactions, neutral beam injection and driven diffusion space. Quasi-linear coefficients derived directly the electric field used calculate distribution functions CQL3D Fokker–Planck code. Alternatively, quasi-linear can be numerically by integrating...
Many high power electronic devices operate in a regime where the current they draw is limited by self-fields of particles. This space charge poses particular challenges for numerical modeling common techniques like over-emission or Gauss' Law are computationally inefficient produce nonphysical effects. In this paper, we show an algorithm using value electric field front surface instead attempting to zero at surface, making particularly well suited both electromagnetic and parallel...
A large diameter thin annular intense relativistic electron beam was modulated at a frequency of 10 GHz. The propagated inside narrow drift tube in which gaps feeding radial cavities were inserted. An external source injected microwave power 180 kW into single input cavity followed by simple idler structure. stable kA rf current modulation induced on the 400 keV beam.
A simple analytic approach for gated field emission array unit cell modeling, the ‘‘Saturn’’ model, has been developed and serves to show how those parameters which most affect inductive output amplifier performance are dependent on material geometry of cell. The Saturn model replaces tip with a sphere gate charged ring. relation then exists between radius, voltage, field, its angular variation sphere, from total emitted current may be given analytically, geometric dependence quantities...
This paper describes the between shots data analysis on TFTR using one-dimensional equilibrium kinetic code SNAP. SNAP accepts as input data: measured plasma size and current, toroidal field, surface voltage, composition (total Zeff contribution from metallic impurities), edge neutral density, auxiliary heating power (neutral beam power, energy, injection geometry and/or rf frequency), profiles of Te(R), ne(R), Ti(R), Vφ(R), Prad(R). iteratively calculates: (1) mapping profile to a minor...
Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation R. J. Dumont, C. K. Phillips, D. N. Smithe; Effects of non-Maxwellian species on ion cyclotron waves propagation absorption in magnetically confined plasmas. Phys. Plasmas 1 April 2005; 12 (4): 042508. https://doi.org/10.1063/1.1881472 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends...
The formation of sheaths near metallic or dielectric-coated wall materials in contact with a plasma is ubiquitous, often giving rise to physical phenomena (sputtering, secondary electron emission, etc) which influence properties and dynamics both far from the material interface. In this paper, we use first-principles PIC simulations such interfaces formulate subgrid sheath boundary condition encapsulates fundamental aspects behavior at Such condition, based on capacitive sheath, shown be...
In an inductive output amplifier, emission-gated electron beam induces high-frequency fields in circuit via displacement current, not convection current. Emission-gated beams experience strong interactions when traversing a resonant or synchronous electromagnetic field, and this interaction is responsible for both the interesting nonlinear physics attractive efficiency compactness of amplifiers. Field emission cathodes, due to their extremely low transit time high transconductance, offer...
The subject of local wave energy in plasmas is treated via quasilinear theory from the dual perspectives action-angle formalism and gyrokinetic analysis. This work presents an extension to all orders gyroradius self-consistent wave-propagation/quasilinear-absorption problem using gyrokinetics. Questions when under what conditions should be definite sign are answered formalism. An important result that 'dielectric operators' linearized equation not same, a fact which obscured eikonal or WKB...
Three dimensional particle-in-cell (PIC) simulations are conducted to measure the space charge limited (SCL) currents in coaxial cylindrical diodes.New cut-cell emission and absorption boundary algorithms implemented electromagnetic PIC code, VORPAL utilized for this study.Comparisons of SCL current results made with i) theoretical one planar diode, ii) analytical solutions two diode cases, iii) an experimental operated as a virtual cathode oscillator.VORPAL show agreement within few percent...
Significant efforts have been made to quantitatively benchmark the sheath sub-grid model used in our time-domain simulations of plasma-immersed antenna near fields, which includes highly detailed three-dimensional geometry, presence slow wave, and non-linear evolution potential. We present both quantitative benchmarking strategy, results for ITER configuration, including maps electric field, potential along entire structure. Our method is based upon a linear plasma [1], using...
Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation John Pasour, David Smithe, Moshe Friedman; The Triaxial Klystron. AIP Conference Proceedings 7 May 1999; 474 (1): 373–385. https://doi.org/10.1063/1.59025 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Dropdown Menu input auto...